FIG. 8A shows cross sectional view of a conventional capacitor element of solid electrolytic capacitor (hereinafter referred to as SEC); FIG. 8B shows front view of the capacitor element. As shown in FIG. 8A, porous anode body 15 is provided by sintering a molded body of valve metal powder, and anode lead wire 16 is buried in anode body 15 with one end protruding out. Outer surface of anode body 15 is covered with dielectric film 17, solid electrolytic layer 18 and cathode layer 19, laminated in the order, to complete a finished capacitor element 14. FIG. 9 shows cross sectional view of a laminate type SEC, which includes conventional capacitor elements 14 stacked for three pieces. As illustrated in the drawing, a plurality of capacitor elements 14 is stacked in the same directional orientation.
Anode lead wire 16 of each capacitor element 14 is connected to external anode terminal 21A. Cathode layer 19 is connected to external cathode terminal 21B. Respective anode leads 16 are connected together with electrical connection member 20. Finally, the entire structure of laminated capacitor elements 14 is covered with insulating resin 22 to make a finished capacitor.
Japanese Patent Laid-Open Application No.2000-306782 discloses a method of providing a thin anode body 15. In the first place, sintered layer 24 is formed on the upper and lower surfaces of valve metal foil 23 which makes anode, as shown in FIG. 10A. Next, sintered layer 24 is stamped out to include valve metal foil 23 which makes anode lead portion, as shown in FIG. 10B. A thin anode body can be manufactured in this way. In a thin anode body for SEC thus manufactured, however, sintered layer 24 formed on valve metal foil 23 which makes anode has been sectioned together with valve metal foil 23 which makes anode lead portion.
As the result, as shown in FIG. 11, the stamped sectional surface has valve metal foil 23 exposed therein. When a dielectric film is provided by anode oxidation, that formed on valve metal foil 23 exposed in the sectioned surface has more defects, as compared with that formed on the surface of sintered layer 24. In the succeeding step of forming a solid electrolyte, the defect portion will have solid electrolyte, which may well be lead to a direct contact with valve metal foil 23. Consequently, the leakage current (LC) tends to increase; in the extreme cases, it resorts to short circuiting. Meanwhile, in the configuration as shown in FIG. 8A and FIG. 8B, where anode lead wire 16 has been buried in anode body 15, volume of anode lead wire 16 is small in relation to that of anode body 15. In the configuration as shown in FIG. 10A and FIG. 10B, where sintered layer 24 is formed on the outer surface of valve metal foil 23, volume of anode lead portion 23 is small in relation to that of sintered layer 24. Consequently, conventional SECs containing the above-described elements have another problem of high ESR (Equivalent Series Resistance) characteristic. Included among the important electrical characteristics with SECs are leakage current, ESR, ESL (Equivalent Series Inductance), etc. The present invention aims to offer an anode body for SEC which is superior in, among other important characteristic items, the leakage current characteristic and the ESR characteristic; and a SEC using the anode body.